APU (Auxiliary Power Unit) ?

What is APU?

A fan asked me to write about APU, so I found out about APU (Auxiliary Power Unit).

An auxiliary power unit is an engine that provides extra power. What do you give? Provides large mobile machines. Now let’s talk about the APU installed on the aircraft.

Aircraft already have an engine, but most are equipped with an APU. The APU can also be used to generate power for the aircraft, as well as other air and hydraulic pressures, whether it is parked on the ground or in an air emergency.

High pressure air, called Bleed Air, is needed to start jet engines. The APU is used to provide passengers with electricity and air-conditioning before departure.

The aircraft’s power requirements are both 115 volt ac 400 Hz and 24 volt DC supplied by the APU. APUs are commonly used in jets. It is also found on some fan aircraft. For example, an aircraft like the Bomberdier Dash 8.
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I want to tell you when the APU was first used. It has been used on British Coast Guard aircraft since World War I. It has 1.75 horsepower (1.30 kw) and is of the ABC type.

It was used for radio transistors, radio transmitters, and emergency air blowers. The first APU to be mounted on a fix wing was a British Supermarine Nighthawk during World War I that attacked German Zeppelins.

During World War II, APUs were installed on US aircraft. Like the B-29 Superfortress. APU model
They are also perfect for four strokes, flat-twin V-twin.

Horsepower up to 7 horsepower. Power up to 28.5 volt 200amp. They are used to start the aircraft’s main engine, starting up to an altitude of 10,000 feet. In flight, it is closed and only wakes up when the plane is about to land.

In 1963, Boeing 727 passenger aircraft began using gas turbine APUs to start main engines in small airports. In modern aircraft, the APU exhaust pipe can be found in the tail.

A systematic analysis of modern APUs consists of three parts.

1 / Power Section

It is the gas generator part of the APU. It compresses a mixture of air and fuel in the chamber and rotates the shaft. Compressed air and oil mix with high energy during combustion, which speeds up the rotation of the shaft.

2 / Load Compressor Section

It connects the compressor to a rotating shaft to generate air pressure. It is equipped with an inlet guide vane and a surge control valve for regulated air flow.

3 / Gearbox Section

In this section, the generators are connected to an axis to generate electricity. Connected via Gearbox. The gearbox also connects to the engine’s fuel control unit, the lubrication module, and the cooling fan.

Later APUs were equipped with starter generator units, which allowed the APU to be started at the push of a button. The steps are not as high as the previous APU old models.

I think you will like this post about APU.